Charging system @ 19 volts

How old is the battery? In general, vehicle batteries are considered 'old' after 5 years especially on bigger engines.
Using a volt meter or a multimeter set to Volts try this. With the engine off and the Keys out test the voltage directly on the battery. You should get a reading somewhere around 12.6 to 13.2 volts. Start the engine and retest the battery voltage. If the alternator is working correctly the reading should rise to somewhere around 13.6 to 14.2 volts.

have the voltage regulator checked
also have the rectifier pack checked in the alternator by using a multimeter that reads ac as well as dc volts
if it is ac volts , replace the alternator
if the voltage regulator is faulty there will not be enough volts to charge a battery
At this point I doubt if it is a short in a circuit but a problem in the charging system

a bad battery would give a wrong judgement of an alternator output. take off your battery and replace with a working one, test your alternator output using a DMM it should read about 12.5 when engine off and 14v when engine start running any figure more or less shows you have a bad alternator or an incorrect input current to the alternator....hope this fixxx it?

One thing you need to check is all the grounds and the positive lead coming from the battery. Cut the insulation back at both ends and check for corrosion. If the wires green or dirty, i'd reccomend replacing the wire. Corrosion on battery wires on the terminals or on the alternator side, will keep the alternator from charging. Make sure the grounds aren't loose and aren't too corroded either. This may not be the problem, but its definitely a probable cause and wouldn't hurt to look. Just my two cents.

if you have the 2.0L non-turbo engine(420a) the voltage is regulated by the PCM(engine ecu). there is no voltage regulator in the alternator.

Your alternator dosent work properly rechaange it again

You dont. Alternators DO NOT require polarisation as they can only be fitted to vehicles that are wired as NEGATIVE EARTH. If you have replaced the Alt, reconnect the wiring, reconnect the battery - Positive lead first then the negative lead, then start the motor !! Using multimeter, check the charge rate at the battery. It should be around 13.8 volts. The charge rate SHOULD NOT go above 14.7 volts and if it does, turn the motor off immediately and recheck the connections, especially any battery voltage sensing wires. if nothing appears to be wrong, contact an auto electrician and have them check things out. I have known faulty regulators, even in new Alternators..

You may have a voltage drop in the battery feed to the Alternator through the fuse link and into the battery. Check the charge rate at the battery feed on the Alternator, it should be at least 13.8 volts, if it is, locate the fuse link and check it there on both sides of the link, if its still good, follow the cable back to the battery checking the voltage as you go. If you find that the voltage suddenly drops across a connection or the fuse link, remove and clean the connection or replace it if possible. If the voltage at the back of the Alternator is less then 13 volts, then the new Alternator may be faulty. If the voltage is higher then 15 volts, then the Battery feed to the Alternator is bad and MUST be fixed. Check these voltages with the engine running but watch out for moving parts ( fans etc). If you think the battery feed to the Alternator is bad, shut the engine down and recheck the voltage at the Alternator, it should be at least the same as it is across the battery. If there is no power to the Alt when the engine is off, start at the fuse link, checking for voltage and trace back to the alt until you lose the reading. If you get no voltage at the fuse link, track it back to the battery. The voltages at the battery and Alternator should be the same or only have a difference of half a volt, any more and you need to locate and fix the bad connection. DO NOT run the Alternator without the load of the battery for extended periods as this will damage the Alternator. The Alt needs the internal resistance of the battery to function correctly. If the voltages from the battery to the alt are correct, check the regulator wiring. If memory serves, there are two small wires to the alt which are in a small plug into the alt and one thick cable which connects to a bolt on the alt. The thick cable is the battery feed, the two small cables are the regulator feeds. One small cable operates the warning lamp in the dash cluster and the other is another battery feed which gives the regulator an indication of the charge rate AT THE BATTERY so if this one is missing the regulator will also cut out. The warning lamp wire serves as an indication to the regulator that the ignition is turned on and makes the alternator charge. This lamp should be on with ignition on but engine NOT running and should go out when you start the engine. If this lamp does not light up at all, suspect a broken or missing warning lamp connection or faulty regulator.A blown warning lamp bulb will also prevent the alt from working, this is because the bulb is fed with power and is grounded at the alt through the regulator and exciter diodes, feeding the regulator with power until the engine starts, then the alternator output essentially puts power to both sides of the diodes causing the lamp to extinguish. A diode is a one way valve for electricity and the regulator is inside the alt. If you suspect a faulty alt or regulator, remove them and have them checked by an autoelectrician. Unless you know what you are doing, DO NOT attempt to disassemble the alt as you can cause catastrophic damage and have to purchase a replacement alt. You may also void any warranty by disassembling the alt.. Undertake these tests and if you have any questions, email me here: [email protected]
Dave.

never mind testing if when you start the car you are getting them voltages then fit a new alternator and quick before you burn out the ECU ,the regulator has packed up end of story ,change alternator now ,NEW not a scrappy one from scrapyard,and stop try to confuse the issue with something you do not know ,no voltage leaving the alternator should not exceed 14.7v

19.8 volts is too high. the alt regulator is not working. The regulator needs a battery source feed to work. Both the feed for the regulator and the connection between the output post and the positive battery terminal should go through an ALT fuse. Start by checking that.